The invention relates to a tool useful for removing fluids and loose material, such as unconsolidated sand, from an earth formation.
In the production of oil and gas various techniques are used to enhance recovery of the petroleum product from earth formations having low permeability. Hydraulic fracturing is an example of such a technique. This procedure involves pumping liquids under high pressure down the well casing and into the producing formation, which fractures the formation outwardly from the well casing. The fractures thus provide a larger surface area in the formation, to enable better drainage of the oil or gas into the well casing.
Following the fracturing operation, loose material, such as unconsolidated sand and other debris, remains in the void created in the formation and also in the perforations in the well casing and the cement jacket. This loose material must be flushed out of the formation and the perforations prior to further treatment, such as gravel packing, to achieve good sand control in the formation.
The tools now available for removing loose materials from a formation are not entirely satisfactory. For example, some of these tools include a rupture disk, so that there is not a full opening through the bore of the tool. In addition, once the disk is ruptured, during removal of material, the disk itself becomes a piece of debris which tends to restrict fluid flow through the tool bore. Another commercially available tool employs a ball valve which is difficult to open because of the high differential pressure between the fluids inside the tool bore and those in the annulus between the well casing and the tool.